Cubic yards and bags of mulch or soil for a garden bed.
AdvertisementA 20x10 ft bed with 3 in of mulch needs about 1.85 cubic yards, or 25 bags of 2 cu ft.
We multiply the bed's length by its width by the depth to get the volume in cubic feet, then convert to cubic yards (27 cu ft each) and divide by the bag size for the number of bags.
2 to 3 in for most beds, and up to 4 in to suppress weeds. Keep mulch a few inches away from tree trunks and plant stems.
One cubic yard is 27 cu ft, so it takes about 13.5 bags of 2 cu ft or 9 bags of 3 cu ft.
One cubic yard covers about 108 sq ft at 3 in deep, 162 sq ft at 2 in, and 81 sq ft at 4 in.
Add about 1 in each year to keep the depth up. Wood mulch breaks down over one to two years, which also feeds the soil.